Celiac disease is characterized by the extreme inability to tolerate gluten proteins found mainly in wheat, barley and rye. It produces symtoms including chronic indigestion, diarrhea, colitis and gas; immune supression; thyroid dysfunction; and skin rashes as well as an articular form of scaly dermatitis. Nutrient absortion is often severely impaired, resulting in dry skin, reduced growth, inability to gain muscle, joint problems and early-onset osteoporosis and osteoarthritis. Furthermore, a high proportion of people with celiac disease seek psychiatric advice, mostly for depression and anxiety.

Gluten sensitivity is indeed known to cause neurological and psychological problems. Central nervous system and peripheral nerve degeneration (fingers, hands, legs, etc.) can also occur, similar to conditions such as diabetic neuropathy, Parkinson's disease and multiple sclerosis.

It is possible to reverse such nerve damage by avoiding gluten for a year or two. For example, a patient suffering from seizures was taking an anticonvulsant medication until it was discovered that he had a severe wheat allergy. After removing wheat from his diet, his seizures resolved without the use of medication. Interestingly, schizophrenia is far less common in countries such as in sub-Saharan Africa where glutenous grains aren't part of the traditional food supply.